More mothers die during labour in richer countries than before.
Deaths of women in and around childbirth have gone down by an average of 35% globally, according to a study using new methods, but are surprisingly high in the United States, Canada and Norway.
The researchers said their findings show it is possible to save women's lives if countries want to and said their analysis should point to ways to do so.
The AIDS pandemic alone, they said, killed more than 61,000 women in and around the time of childbirth in 2008, most of them in Africa.
"These findings are very encouraging and quite surprising. There are still too many mothers dying worldwide, but now we have a greater reason for optimism than has generally been perceived," said Dr. Christopher Murray of the Institute for Health Metrics and Evaluation at the University of Washington, who led the study.
The findings contradict work done by the World Health Organization, which reported last May that mothers and newborns are no more likely to survive now than 20 years ago.
Murray and colleagues took every bit of data they could find on deaths of women from records in 181 countries and plugged this information into a computer model.
They found the number of women dying from pregnancy-related causes has dropped by more than 35% globally in the past 30 years.
"One of the most surprising results is the apparent rise in the maternal mortality rate in the USA, Canada, and Norway," they added. But it can partly be because US death certificates recently started asking about pregnancy, they added.
But this does not explain why US maternal deaths are double the rates in Britain, triple the rates in Australia and four times the rate in Italy, they said.
In the United States the rate rose from 12 deaths per 100,000 live births in 1980 to 17 in 2008. In Canada, the rate hovered between 6 and 7 for the whole time and Norway's rose from 7 per 100,000 in 1980 to 8 per 100,000 in 2008.
"Progress overall would have been greater if the HIV epidemic had not contributed to substantial increases in maternal mortality in eastern and southern Africa," they added.
Nearly one out of every five maternal deaths or a total of 61,400 in 2008, were associated with AIDS infections.
About 80% of all deaths of pregnant women or new mothers were in 21 countries, with half of all such deaths in just six countries - India, Nigeria, Pakistan, Afghanistan, Ethiopia, and the Democratic Republic of the Congo.
"Finding out why a country such as Egypt has had such enormous success in driving down the number of women dying from pregnancy-related causes could enable us to export that success to countries that have been lagging behind," Murray said. Why do you think more women in labour are dying in richer countries?